Method for allocating authorization key identifier for wireless portable internet system

ABSTRACT

A method and authentication apparatus for sharing information for identifying an Authorization Key (AK) with a Base Station (BS) in a subscriber station are provided. The method includes, in the subscriber station, sharing a root key with the BS by performing an authentication with the BS, sharing an AK derived from the root key with the BS, sharing an AK sequence number of the AK with the BS, and sharing an AK Identifier (AKID) of the AK with the BS. The AK sequence number is generated by a sequence number of the root key. The AKID is generated by a parameter including the AK, the AK sequence number, a Medium Access Control (MAC) address of the subscriber station, and a BS Identifier (BSID) of the BS.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patent application Ser. No. 11/908,211, filed on Sep. 10, 2007, which was a US national stage entry of an international application No. PCT/KR2005/003593 filed on Oct. 27, 2005, and claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2005-0054055, filed on Jun. 22, 2005 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an authentication method in a wireless portable Internet system, and more specifically, to a method for allocating an authorization key identifier in the wireless portable Internet system.

2. Description of the Related Art

Wireless portable Internet supports mobility in local area data communication such as in a conventional wireless Local Access Network (LAN) that uses a fixed access point, which is a next-generation communication system. Various standards for the wireless portable Internet have been proposed, and the international standard of the wireless portable Internet has progressed in the IEEE 802.16e. The above-described IEEE 802.16 supports the Metropolitan Area Network (MAN) representing an information communication network covering the LAN and the Wide Area Network (WAN).

To securely provide various traffic data services in a wireless portable Internet system, it is required to perform a security function including authentication and authorization functions. In addition, the above functions are required to guarantee network stability and stability of the wireless portable Internet service. Recently, a Privacy Key Management version 2 (PKMv2) which is security key management protocol has been proposed to provide higher security. In the PKMv2, subscriber station equipment authentication, base station equipment authentication, and user authentication may be performed in a Rivest Shamir Adleman (RSA) authentication method or an Extensible Authentication Protocol (EAP) authentication method. The subscriber station and the base station share an authorization key in the above RSA and EAP authentication methods.

In further detail, a method for allocating an authorization key identifier in a conventional IEEE 802.16 wireless Metropolitan Area Network (MAN) system will be described.

Firstly, in the RSA-based authorization method, when an RSA based authorization is achieved, the subscriber station and the base station share a Primary Authorization Key (PAK). At this time, an identifier for the shared PAK is sequentially generated by the base station, and is transmitted to the subscriber station. In addition, an authorization key identifier which is an identifier for an authorization key yielded from the PAK has a value that is equal to that of the PAK identifier.

In the EAP-based authorization method, when an EAP-based authorization is achieved, the subscriber station and the base station share a Pairwise Master Key (PMK). When the subscriber station and the base station share the PMK yielded from the EAP-based authorization, an identifier for the shared PMK has a value yielded from an EAP session ID value. In this case, the subscriber station and the base station receive the EAP session ID value from higher EAP protocol.

In addition, an authorization key Identifier which is an identifier for an authorization key generated by the PMK has a value that is generated from the same EAP Session ID value.

While the subscriber station and the base station share the authorization key from the above methods, the subscriber station and the base station respectively have the two PAKs and two authorization keys when re-authentication is performed by the RSA-based authorization method. In this case, since the base station allocates the respective PAK identifier and authorization key identifier, the PAKs may be identified by the two PAK identifiers, and the two authorization keys may be identified by the two authorization key identifiers.

In addition, when the re-authentication is performed by the EAP-based authorization method, the subscriber station and the base station respectively have the two authorization keys. In this case, it is required to identify the two authorization keys by using the authorization key identifiers respectively generated by the subscriber station and the base station with the EAP session ID value. However, since the EAP session ID value used as input data for generating the authorization key identifier by the subscriber station and the base station is not changed even when the EAP-based re-authentication is performed, the new authorization key identifier is equal to the previous authorization key identifier and the new PMK identifier is equal to the previous PMK identifier. Moreover, the subscriber station and the base station respectively have the two PMKs and the two authorization keys, and problematically. These keys may not be distinguished. Therefore, there is a problem in that the two PMKs and the two authorization keys in a re-authentication process may not be distinguished by the PMK identifier and the authorization key identifier used in the EAP-based authorization method.

In addition, with the authorization key identifier of the conventional IEEE 802.16 wireless MAN system-based wireless portable Internet system, there is a problem in that a lot of resources are consumed to transmit Medium Access Control (MAC) messages including the PAK, PMK, and authorization key identifiers since sizes of the identifiers are large.

Therefore, the identifiers for the PAK, PMK, and authorization key shared by the subscriber station and the base station are required to identify respective keys, and the sizes of the identifiers are required to be efficiently reduced.

The above Information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide a method for easily identifying more than two authorization keys, and allocating an identifier which is efficiently reduced in size.

In an exemplary method performed by a base station according to an embodiment of the present invention, an identifier for identifying an authorization key shared with a subscriber station in a wireless portable Internet system is allocated. In the exemplary method, a) an authentication is performed with the subscriber station and the authorization key is shared with the subscriber station; b) an authorization key identifier for identifying the authorization key is generated, the authorization key identifier is transmitted to the subscriber station, and the authorization key identifier is shared with the subscriber station; c) the authentication is performed with the Subscriber station in response to a re-authentication request of the subscriber station and a new authorization key is shared with the subscriber station; and d) another authorization key identifier for identifying the new authorization key is generated. The authorization key identifier is transmitted to the subscriber station, and the authorization key identifier is shared with the subscriber station.

In an exemplary method performed by a subscriber station according to another embodiment of the present invention, an identifier for identifying an authorization key shared with a base station in a wireless portable Internet system is allocated. In the exemplary method, a) an authentication is performed with the base station and the authorization key is shared with the base station; b) an authorization key identifier for identifying the authorization key is received from the base station and the authorization key identifier is shared with the base station; c) a re-authentication is requested to the base station, the authentication is performed with the base station, and a new authorization key is shared with the base station, and d) another authorization key identifier for identifying the new authorization key is received from the base station and the authorization key Identifier is shared with the base station.

In an exemplary method performed by a base station according to a further embodiment of the present invention, an identifier for identifying the authorization key shared with a subscriber station in a wireless portable Internet system is allocated.

In the exemplary method, a) an authentication is performed with the subscriber station and the authorization key is shared with the subscriber station; b) an authorization key identifier for identifying the authorization key is shared with the subscriber station (the authorization key identifier is generated by a predetermined authorization key sequence number that is generated by the base station and is transmitted to the subscriber station); c) the authorization is performed in response to a re-authentication request from the subscriber station and a new authorization key is shared with the subscriber station; and d) a new authorization key identifier for identifying the new authorization key is shared with the subscriber station (the new authorization key Identifier is generated by a new authorization key sequence number that is generated by the base station and is transmitted to the subscriber station).

In an exemplary method performed by a subscriber station according to a still further embodiment of the present invention, an Identifier for identifying an authorization key shared with a base station in a wireless portable Internet system is allocated.

In the exemplary method, a) an authentication is performed with the base station and the authorization key is shared with the base station; b) an authorization key identifier for Identifying the authorization key is shared with the base station (the authorization key identifier is generated by a predetermined authorization key sequence number that is generated by the base station and is transmitted to the subscriber station); c) a re-authentication is requested to the base station, the authentication is performed with the base station. and a new authorization key is shared with the base station; and d) a new authorization key identifier for identifying the new authorization key is shared with the base station (the new authorization key identifier is generated by a new authorization key sequence number that is generated by the base station and is transmitted to the subscriber station).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram representing a wireless portable 20 Internet according to an exemplary embodiment of the present invention.

FIG. 2 shows a table representing a configuration of parameters related to the authorization keys in the wireless portable Internet system according to the first exemplary embodiment of the present invention.

FIG. 3 shows a flowchart representing an authentication process based on the RSA-based authorization method in the wireless portable Internet system according to the first exemplary embodiment of the present invention.

FIG. 4 shows a flowchart representing an authentication process based on the EAP-based authentication method in the wireless portable Internet system according to the first exemplary embodiment of the present invention.

FIG. 5 shows a table of parameters related to authorization keys of the PKMv2 in the wireless portable Internet system according to the second exemplary embodiment of the present invention.

FIG. 6 shows a flowchart representing an authentication process according to the RSA-based authorization policy in the wireless portable Internet system according to the second exemplary embodiment of the present invention.

FIG. 7 shows a flowchart representing the authentication process according to the EAP-based authorization policy in the wireless portable Internet system according to the second exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

FIG. 1 shows a schematic diagram representing a wireless portable Internet according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a wireless portable Internet system includes a subscriber station 10, base stations 20 and 21 for performing wireless communication with the subscriber station 10, routers 30 and 31 accessed to the base stations 20 and 21 through gateways, and an Authentication, Authorization, and Accounting (AAA) server 40 accessed to the routers 30 and 31 to authenticate the subscriber station 10 and a user.

An authorization policy performed by the subscriber station 10 and the base station 20 according to the exemplary embodiment of the present invention is based on a Privacy Key Management version 2 (PKMv2). Authorization policies based on the PKMv2 are classified into three types. The first type is a Rivest Shamir Adleman (RSA)-based authentication method 20 for performing mutual equipment authorization of the subscriber station 10 and the base station 20, and the second type is an Extensible Authentication Protocol (EAP)-based authentication method for performing the subscriber station equipment authentication and the base station equipment authentication and user authentication by using a higher EAP protocol. In addition, there is a combination of the two methods, in which the RSA-based authorization method for the subscriber station equipment authentication and the base station equipment authentication is performed and then the EAP-based authorization for the user authentication is performed. The third type is an authenticated EAP-based authorization method performed by using a key yielded from the RSA-based authorization method or the EAP-based authorization method after performing the RSA-based authorization or the EAP-based authorization for the subscriber station equipment authentication and the base station equipment authentication.

A method for allocating an authorization key identifier according to a first exemplary embodiment of the present invention, based on the above authorization policies, will now be described.

FIG. 2 shows a table representing a configuration of parameters related to the authorization keys in the wireless portable Internet system according to the first exemplary embodiment of the present invention, and FIG. 3 shows a flowchart representing an authentication process based on the RSA-based authorization method in the wireless portable Internet system according to the first exemplary embodiment of the present invention.

Referring to FIG. 2 and FIG. 3, when the subscriber station 10 and the base station 20 use the RSA-based authorization method as the authentication method in the wireless portable Internet system according to the first exemplary embodiment of the present invention, a PKMv2 RSA-Request message 611, a PKMv2 RSA-Reply message 612, and a PKMv2 RSA-Acknowledgement message 613 are used between the subscriber station 10 and the base station 20.

Firstly, the subscriber station 10 adds a certificate of the subscriber station 10 into the PKMv2 RSA-Request message 611 to perform an authentication process according to the RSA-based authorization policy.

The base station 20 receiving the PKMv2 RSA-Request message 611 from the subscriber station 10 performs the equipment authentication of the subscriber station 10, and when the equipment authentication of the subscriber station is successfully achieved, the base station 20 transmits the PKMv2 RSA-Reply message 612 including a certificate of the base station and a pre-Primary Authorization Key (pre-PAK) encrypted with a public key of the subscriber station 10 to the subscriber station 10.

The subscriber station 10 receiving the PKMv2 RSA-Reply message 612 from the base station 20 authenticates the certificate of the base station 20, and when the equipment authentication of the base station 20 is successfully achieved, the subscriber station 10 transmits the PKMv2 RSA-Acknowledgement message 613 to the base station 20. Accordingly, the RSA-based mutual authentication process is finished.

The subscriber station 10 and the base station 20 may share the pre-PAK₁ in the above process, respectively generate a PAK₁ by using the pre-PAK₁ and share the PAK₁. In addition, since the subscriber station 10 and the base station 20 generate an authorization key AK1 by using the shared PAK₁, they share the same AK1.

Since the base station 20 generates a PAK sequence number PAK_SN₁ for identifying the PAK₁, and transmits the PKMv2 RSA-Reply message 612 including the PAK sequence number to the subscriber station 10, the subscriber station 10 and the base station 20 share the PAK sequence number PAK_SN₁. In this case, the size of the PAK sequence number PAK_SN₁ shared by the subscriber station 10 and the base station 20 is 8 bits. That is, the base station 20 generates and distributes the 8 bit-PAK sequence number PAK_SN₁ to the subscriber station 10, and in further detail, the most significant 4 bits among the 8 bit-PAK sequence number PAK_SN₁ are set to be 0 and the remaining least significant 4 bits are set to be valid. In addition, whenever the PAK is updated, the least significant 4 bits are increased by one by the base station 20, and modulo 16 is applied to the least significant 4 bits.

In addition, since the base station 20 transmits a PAK lifetime to the 15 subscriber station 10 while transmitting the PKMv2 RSA-Reply message 612 to the subscriber station 10, the subscriber station 10 and the base station 20 share the PAK lifetime.

After the RSA-based authorization is achieved, a 3-way SA-TEK exchange process is performed between the subscriber station 10 and the base station 20 so that the subscriber station 10 and the base station 20 may be informed of an AK sequence number which is an identifier of the AK, a Security Association Identifier (SA-ID), and algorithms used for each SA.

Firstly, the base station 20 generating the AK in the RSA-based authorization method transmits a PKMv2 SA-TEK-Challenge message 614 including the authorization key sequence number AK_SN₁ and the lifetime to the subscriber station 10.

The subscriber station 10 receiving the PKMv2 SA-TEK-Challenge message 615 transmits a PKMv2 SA-TEK-Request message 315 to inform the base station 20 of supportable encryption algorithms. Subsequently, the base station 20 receiving the PKMv2 SA-TEK-Request message 615 from the subscriber station 10 informs the subscriber station 10 of the SA-IDs and algorithms corresponding to a supportable primary SA and a plurality of static SAs by transmitting a PKMv2 SA-TEK-Response message 616, and the 3 way SA-TEK exchange process is finished.

Accordingly, the subscriber station 10 and the base station 20 share the AK sequence number AK_SN₁, and the size of the shared AK sequence 15 number AK_SN₁ is 8 bits. That is the base station 20 generates and distributes the 8 bit-AK sequence number AK_SN₁ to the subscriber station 10, and in further detail, the most significant 4 bits among the 8 bit-AK sequence number AK_SN₁ are set to be 0 and the remaining least significant 4 bits are set to be valid. In addition, whenever the AK is updated, the least significant 4 bits are increased by one by the base station 20, and modulo 16 is applied to the least significant 4 bits.

In addition, the subscriber station 10 is required to perform RSA-based re-authentication before the PAK lifetime shared with the base station 20 expires.

Accordingly, the subscriber station 10 transmits a PKMv2 RSA-Request message 611-1 to the base station 20 to perform the RSA-based re-authentication.

The base station 20 receives a re-authentication request from the subscriber station 10, allocates a pre-PAK₂ for generating a new PAK₂ and a PAK sequence number PAK_SN₂ for identifying the new PAK₂, and transmits the pre-PAK₂ and PAK sequence number PAK_SN₂ to the subscriber station 10 by using a PKMv2 RSA_Reply message 612-1.

Subsequently, when the subscriber station 10 receiving the PKMv2 RSA-Reply message 612 from the base station 20 successfully achieves the equipment authentication of the base station 20, the subscriber station 10 transmits a PKMv2 RSA-Acknowledgement message 613-1 to the base station 20, and the RSA-based re-authentication process is finished.

Therefore, since the subscriber station 10 and the base station 20 share the PAK₂ and the PAK sequence number PAK_SN₂ generated by performing the re-authentication, and generate an authorization key AK₂ by using the PAK₂, they may share the same AK₂.

The base station 20 sets the PAK sequence number PAK_SN₂ to be 8 bits in a like manner of the PAK sequence number PAK_SN₁. In addition, whenever the RSA-based authorization process is successfully achieved and then the new PAK sequence number PAK_SN₁ is generated, the least significant 4 bits of the PAK sequence number PAK_SN₂ are increased by one and modulo 16 is applied to the least significant 4 bits. That is, when the previous PAK sequence number PAK_SN₁ is ‘00001001’ the newly allocated PAK sequence number PAK_SN₂ becomes ‘00001010’. When the RSA-based re-authentication is successfully achieved as described above, the subscriber station 10 and the base station 20 respectively have the two PAKs, PAK₁ and PAK₂, before the previous PAK sequence number PAK_SN₁ expires. Since the subscriber station 10 and the base station 20 have the different PAK sequence numbers PAK_SN₁, PAK_SN₂ for each PAK, they may easily identify the two PAKs.

In addition, after performing the RSA-based re-authentication process, the subscriber station 10 and the base station 20 perform the 3-Way SA-TEK process.

The base station 20 having the generated AK₂ by performing the RSA-based re-authentication transmits a PKMv2 SA-TEK-Challenge message 614-1 including an authorization key sequence number AK_SN₂ corresponding to an authorization key identifier for identifying the AK₂ to the subscriber station 10.

Subsequently, the subscriber station 10 receiving the PKMv2 SA-TEK-Challenge message 614-1 transmits a PKMv2 SA-TEK-Request 20 message 615-1 to inform the base station 20 of supportable encryption algorithms and then the base station 20 transmits a PKMv2 SA-TEK-Response message 316-1 to inform the subscriber station 10 of the SA-IDs and the algorithms corresponding to a supportable primary SA and a plurality of static SAs, and then the 3-Way SA-TEK process for performing the re-authentication is finished.

In the above process, the subscriber station 10 and the base station 20 share the authorization key sequence number AK_SN₂ for the AK₂ and 5 the authorization key sequence number AK_SN₂ is set to be 8 bits in a like manner of the previous authorization key sequence number AK_SN₁. When the base station 20 generates and distributes the authorization key sequence number AK_SN₂ to the subscriber station 10, the least significant 4 bits of the authorization key sequence number AK_SN₂ are increased by one whenever the new authorization key sequence number AK_SN₂ is generated and modulo 16 is applied to the least significant 4 bits. For example, when the previous authorization key sequence number PAK_SN₁ is ‘00000011’, the newly allocated authorization key sequence number AK_SN₂ is ‘00000100’. When the RSA-based re-authentication is successfully achieved, the subscriber station 10 and the base station 20 respectively have the two AKs, AK₁ and AK₂ before the previous authorization key sequence number AK_SN1 expires. Since the subscriber station 10 and the base station 20 have the different AK sequence numbers AK_SN₁ and AK_SN₂ for each AK, they may easily identify the two AKs.

FIG. 4 shows a flowchart representing an authentication process based on the EAP-based authentication method in the wireless portable Internet system according to the first exemplary embodiment of the present invention.

Referring to FIG. 2 and FIG. 4, when the subscriber station 10 and the base station 20 use the EAP-based authorization method in the wireless portable Internet system according to the first exemplary embodiment of the present invention, a PKMv2 EAP-Start message 411 and a PKMv2 EAP-Transfer message 412 are used between the subscriber station 10 and the base station 20. In addition, a PKMV2 EAP-Transfer-Complete message 413 may be selectively used.

Firstly, the subscriber station 10 transmits the PKMv2 EAP-start message 411 to the base station 20 to notify a start of the EAP-based authorization process to the EAP method protocol.

The base station 20 receiving the PKMv2 EAP-start message 411 notifies the start of the EAP-based authorization process to the EAP method protocol of a network. Then, the PKMv2 EAP-Transfer message 412 is transmitted several times between the subscriber station 10 and the base station 20 according to a process of the EAP method protocol. That is, Medium Access Control (MAC) layers of the base station 20 and the subscriber station 10 transmit an EAP payload used in the EAP method to a peer node by using the PKMv2 EAP-Transfer message 412. When the EAP-based authorization is successfully achieved, the subscriber station 10 transmits the PKMV2 EAP-Transfer-Complete message 413 to inform the base station 20 that the EAP-based authorization is finished. The EAP-based authorization process may be finished without transmitting the PKMV2 EAP-Transfer-Complete message 413 in some cases.

When the used EAP method is a key generation protocol such as a Transport Layer Security (EAP-TLS), the subscriber station 10 and the base station 20 may share an AAA-key₁ in the EAP-based authorization process, generate Pairwise Master Keys (PMK₁) with the AAA-key₁, and share the PMK₁. In addition, since the subscriber station 10 and the base station 20 generate the AK₁ by using the shared PMK₁ they may share the same AK₁.

After the EAP-based authorization is achieved, the 3-Way SA-TEK exchange process is performed between the subscriber station 10 and the base station 20 so that the subscriber station 10 and the base station 20 may be aware of the AK sequence number which is the identifier of the AK the SA-ID, and the algorithms for each SA.

Firstly, the base station 20 having the generated AK₁ in the EAP-based authorization method transmits a PKMv2 SA-TEK-Challenge message 414 including the PMK lifetime and the authorization key sequence number AK_SN1 to the subscriber station 10.

Accordingly, the subscriber station 10 and the base station 20 may share the PMK lifetime. In this case, since the base station 20 receives the PMK lifetime from the EAP method protocol or uses a value defined by a vendor as the PMK lifetime, the PMK lifetime may be allocated in all cases.

The subscriber station 10 receiving the PKMv2 SA-TEK-Challenge message 414 transmits a PKMv2 SA-TEK-Request message 415 to notify the supportable encryption algorithms to the base station 20.

The base station 20 receiving the PKMv2 SA-TEK-Request message 415 from the subscriber station 10 transmits a PKMv2 SA-TEK-Response message 416 to inform the subscriber station 10 of the SA-IDs and the algorithms corresponding to a supportable primary SA and a plurality of static SAs to the subscriber station 10, and then the 3-Way SA-TEK exchange process is finished.

In the above process, the subscriber station 10 and the base station 20 may share the authorization key sequence number AK_SN₁, and the size of the authorization key sequence number AK_SN₁ is 8 bits. That is, the base station 20 generates and distributes the 8 bit-authorization key sequence number AK_SN₁ to the subscriber station. In further detail, the most significant 4 bits among the 8 bit-authorization key sequence number AK_SN₁ are set to be 0, and the remaining least significant 4 bits are set to be valid. In addition, the least significant 4 bits are increased by one and modulo 16 is applied to the least significant 4 bits.

In addition, the EAP-based re-authentication is required to be performed by the subscriber station 10 and the base station 20 before the shared PMK lifetime expires.

For performing the EAP-based re-authentication, the subscriber station 10 transmits a PKMv2 EAP-start message 411-1 to the base station 20 to notify the start of the EAP-based re-authentication process to the EAP method protocol of the network.

The base station 20 receiving the PKMv2 EAP-start message 411-1 notifies the start of the EAP-based re-authentication process to the EAP method protocol of the network. Subsequently, a PKMv2 EAP-Transfer message 412-1 is transmitted several times between the subscriber station 10 and the base station 20 according to the process of the EAP method protocol. When the EAP-based authorization is successfully achieved, the subscriber station 10 transmits a PKMV2 EAP-Transfer-Complete message 413-1 to the base station 20 to inform the base station 20 that the EAP-based authorization is finished. The EAP-based authorization may be finished without transmitting the PKMV2 EAP-Transfer-Complete message 413-1 in some cases.

In the above process, since the subscriber station 10 and the base station 20 share an AAA-key₂, and the subscriber station 10 and the base station 20 respectively generate a new PMK₂ by using the AAA-key₂ and share the PMK₂. In addition, since the subscriber station 10 and the base station 20 generate the new authorization key AK₂ by using the shared PMK₂, they may share the same AK₂. In the EAP-based authorization method, since the previous PMK₁ is eliminated and the new PMK₂ is used in the higher EAP method protocol when the new PMK₂ is generated and shared after the re-authentication is performed, it is not required to additionally provide identifiers for identifying the two PMKs (i.e., PMK₁ and PMK₂) in the MAC layers of the subscriber station 10 and the base station 20 when characteristics of the EAP method protocol are applied. That is, it is not required to additionally define the PMK identifier.

In addition, the subscriber station 10 and the base station 20 perform the 3-Way SA·TEK exchange process for performing the re-authentication after finishing the EAP-based re-authentication process.

The base station 20 having the generated AK₂ by performing the EAP-based re-authentication transmits a PKMv2 SA-TEK-Challenge message 414-1 including the authorization key sequence number AK_SN₂ corresponding to the authorization key identifier for identifying the new AK₂ and the PMK lifetime to the subscriber station 10.

The subscriber station 10 receiving the PKMv2 SA-TEK-Challenge message 414-1 transmits a PKMv2 SA-TEK-Request message 415-1 to the base station 20 to notify the supportable encryption algorithms to the base station 20 and then the base station 20 transmits a PKMv2 SA-TEK-Response message 416-1 to the subscriber station 10 to Inform the subscriber station 10 of the SA-IDs and the algorithms corresponding to a supportable primary SA and a plurality of static SAs, and therefore the 3-Way 15 SA-TEK exchange process is finished.

In the above process, the subscriber station 10 and the base station 20 share the authorization key sequence number AK_SN₂ for the new AK₂, and the shared authorization key sequence number AK SN₂ is set to be 8 bits in a like manner of the previous authorization key sequence number AK_SN₁. In this case, when the base station 20 generates and distributes the authorization key sequence number AK_SN₂ to the subscriber station 10, the least significant 4 bits of the authorization key sequence number AK_SN₂ are increased by one whenever the new authorization key sequence number AK_SN₂ is generated and modulo 16 is applied to the least significant 4 bits. For example, when the previous authorization key sequence number AK_SN₁ is ‘00000010’, the newly allocated authorization key sequence number AK_SN₂ becomes ‘00000011’. When the EAP-based re-authentication is successfully achieved as described above, the subscriber station 10 and the base station 20 respectively have the two AKs, AK₁ and AK₂ before the previous authorization key sequence number AK_SN₁ expires. Since the subscriber station 10 and the base station 20 have the different AK sequence numbers AK_SN₁ and AK_SN₂ for each AK, they may easily identify the two AKs.

As described above, a problem of the defined identifiers of the respective keys (e.g., the PAK identifier and the authorization key identifier) and the PMK lifetime in the PKMv2 of the conventional IEEE 802.16e wireless MAN-based portable Internet service is resolved according to the first exemplary embodiment of the present invention. That is, when the lifetime for key is provided in the EAP method protocol, this lifetime is used as the PMK lifetime, but when the lifetime for key is not provided in the EAP method protocol, the lifetime defined by the vendor is used as the PMK lifetime. Therefore, the EAP-based re-authentication may be efficiently performed.

In addition, since the sizes of the PAK identifier and the authorization key identifier are reduced from 64 bits to 8 bits, the efficiency is increased when the identifier is transmitted in a radio link.

Further, the base station 20 generates the authorization key identifier derived from the PMK not by using the EAP session ID value but by increasing the authorization key identifier by one whenever the authorization key is updated and allocates the authorization key identifier to the subscriber station 10. Therefore, the two authorization keys are distinguished by the authorization key identifier.

It has been described that one of the RSA-based authorization process and the EAP-based authorization process is performed, and hereinafter it will be described that the RSA-based authorization process and the EAP-based authorization process or the authenticated EAP-based authorization process are simultaneously performed.

When the RSA-based authorization process and the EAP-based authorization process or the authenticated EAP-based authorization process are performed, referring to FIG. 3, the base station 20 and the subscriber 15 station 10 may share the PAK1, PAK lifetime and the PAK sequence number PAK_SN₁ in RSA-based authorization process 311, 312, and 313 as described above, and subsequently, referring to FIG. 4, they may share the PMK₁ in EAP-based authorization process 411, 412, and 413 as described above. In case that the authenticated EAP-based authorization process is performed rather than performing the EAP-based authorization processes 411, 412, and 413, they may share the PMK₁ in the authenticated EAP-based authorization process.

The PKMv2 EAP-Start message 411 and the PKMv2 EAP. Transfer-Complete message 413 as an optional message are used in the authenticated EAP-based authorization process. A PKMv2 Authenticated-EAP-Transfer message including a message authentication function is used rather than using the PKMv2 EAP-Transfer message 412 of the EAP authentication process. Since the authorization key AK₁ is generated by combining the shared PAK₁ and PMK₁, the subscriber station 10 and the base station 20 may share the AK₁. In this case, the size of the PAK sequence number PAK_SN₁ shared by the subscriber station 10 and the base station 20 is 8 bits, the most significant 4 bits are set to 0, and the least significant 4 bits are set to be valid. However, there is no PMK identifier.

Subsequently, referring to FIG. 3 and FIG. 4, the base station 20 generates the authorization key sequence number AK_SN₁ in the 3-Way SA-TEK exchange process and allocates the AK_SN₁ to the subscriber station 10. In this case, the size of the authorization key sequence number AK_SN₁ shared by the subscriber station 10 and the base station 20 is 8 bits, the most significant 4 bits are set to be 0, and the least significant 4 bits are set to be valid.

The subscriber station 10 and the base station 20 may share the PAK lifetime in the RSA-based authorization process, and share the PMK lifetime in the 3-Way SA-TEK exchange process.

Since the PAK lifetime and the PMK lifetime have separate values when the RSA-based authorization process and the EAP-based authorization process or the authentication EAP-based authorization process are concurrently performed as describes above, the RSA-based re-authentication process or the EAP-based re-authentication process may be independently performed.

When the RSA-based re-authentication process is performed before the PAK lifetime expires, the subscriber station 10 and the base station 20 may share a new PAK₂ and a PAK sequence number PAK_SN₂ in the RSA-based re-authentication process, share the new authorization key sequence number AK_SN₂ in the 3-Way SA-TEK exchange process subsequently performed after the RSA-based re-authentication process, and use the existing shared PMK₁ to generate and share a new authorization key AK₂.

In addition, the EAP-based re-authentication process is performed before the PMK lifetime expires, the subscriber station 10 and the base station 20 share the new PMK₂ in the EAP-based re-authentication process, share the new authorization key sequence number AK_SN₂ in the 3-Way SA·TEK exchange process that is subsequently performed after the EAP-based re-authentication process, and use the existing shared PAK₁ and PAK sequence number PAK_SN₁ to generate and share the new authorization key AK₂.

When the various re-authentication processes are performed as described above, the two PAKs, PAK₁ and PAK₂, may be identified by using the PAK sequence numbers PAK_SN₁ and PAK_SN₂, and the two authorization keys AK₁ and AK₂ may be identified by using the authorization key sequence numbers AK_SN₁ and AK_SN₂. Here, according to characteristics of the higher EAP authentication protocol, the existing PMK₁ is discarded to use the new PMK₂ when the new PMK₂ is generated in the EAP-based re-authentication process. Accordingly, the PMK identifier is not necessary since the subscriber station 10 and the base station 20 share only one PMK at any moment when the characteristic of the higher EAP authorization protocol is applied to the MAC layers of the subscriber station 10 and the base station 20. In this case, the sizes of the PAK sequence number PAK_SN₂ and the authorization key sequence number AK_SN₂ are 8 bits.

The re-authentication processes may be easily understood by referring to FIG. 3 and FIG. 4, and therefore detailed descriptions thereof will be omitted.

As described above, the problems of the respective key identifiers and the PMK lifetime defined in the PKMv2 of the conventional IEEE 802.16e wireless MAN-based portable Internet service are resolved according to the first exemplary embodiment of the present invention. That is, when the lifetime for key is provided In the EAP method protocol, this lifetime is used as the PMK lifetime, but when the lifetime for key is not provided in the EAP method protocol, the lifetime defined by the vendor is used as the PMK lifetime. Therefore, the EAP-based re-authentication may be efficiently performed.

In addition, the efficiency is increased when the identifier is transmitted in the radio link since the sizes of PAK identifier and authorization key identifier are reduced from 64 bits to 8 bits.

A method for allocating the authorization key identifier according to a second exemplary embodiment of the present invention will now be described.

FIG. 5 shows a table of parameters related to authorization keys of the PKMv2 in the wireless portable Internet system according to the second exemplary embodiment of the present invention, and FIG. 6 shows a flowchart representing an authentication process according to the RSA-based authorization policy in the wireless portable Internet system according to the second exemplary embodiment of the present invention.

A method for allocating the authorization policy. the authorization keys, and the respective authorization key identifiers according to the second exemplary embodiment of the present invention is similar to that of the first exemplary embodiment of the present invention described with reference to FIG. 2 to FIG. 4, and therefore parts that are different from the first exemplary embodiment of the present invention will be described in the second exemplary embodiment of the present invention.

Referring to FIG. 5 and FIG. 6, when the subscriber station 10 and the base station 20 select an RSA-based authorization method as an 20 authorization policy in the wireless portable Internet system according to the second exemplary embodiment of the present invention, the subscriber station 10 and the base station 20 use a PKMv2 RSA-Request message 811, a PKMv2 RSA-Reply message 812, and a PKMv2 RSA-Acknowledgement message 813 to perform the mutual authentication of the base station 20 and subscriber station 10.

When the authentication of the base station 20 and subscriber station 10 is successfully performed, the subscriber station 10 and the base station 20 may share the pre-PAK₁, PAK lifetime, and PAK sequence number PAK_SN₁ by using the PKMv2 RSA-Reply message 812. In addition, since the subscriber station 10 and the base station 20 respectively generate and share the PAK₁ by using the pre.PAK₁, and generate the authorization key AK₁ by using the generated PAK₁, they may share the same AK₁. In this case, the size of the PAK sequence number PAK_SN1 shared by the subscriber station 10 and the base station 20 is 4 bits. That is, the base station 20 generates the PAK sequence number PAK_SN₁ as 4 bits and allocates it to the subscriber station 10. In further detail, the most significant 2 bits are set to be 0, and the least significant 2 bits are set to be valid. In addition, whenever the PAK is updated, the least significant 2 bits are increased by one and modulo 4 is applied to the least significant 2 bits.

In addition, the subscriber station 10 and the base station 20 may share the authorization key sequence number AK_SN₁ in the 3-Way SA-TEK exchange process, particularly by using the PKMv2 SA-TEK-Challenge 20 message 814 in a like manner of the first exemplary embodiment of the present invention. However, differing from the first exemplary embodiment of the present invention, the authorization key sequence number AK_SN₁ is allocated to be the same as the PAK sequence number PAK_SN₁ in the second exemplary embodiment of the present invention. That is, the base station 20 uses the allocated PAK sequence number PAK_SN₁ as the authorization key sequence number AK_SN₁ when it generates the authorization key sequence number AK_SN₁ and distributes the AK_SN₁ to the subscriber station 10. Therefore, the size of the authorization key sequence number AK_SN₁ is 4 bits. In further detail, among the 4 bit-authorization key sequence number AK_SN₁ the most significant 2 bits are set to be 0, and the remaining least significant 2 bits are set to be equal to that of the PAK sequence number PAK_SN₁.

Another difference between the first and second exemplary embodiments of the present invention is that an authorization key identifier AKID₁ is used rather than using the authorization key sequence number AK_SN₁ to identify the authorization key, and the authorization key identifier AKID₁ is generated by using the authorization key sequence number AK_SN₁, the authorization key AK₁, a Subscriber Station MAC address SSID, and a Base Station identifier BSID which has been shared or known. Since the subscriber station MAC address SSID and the base station identifier BSID are previously noticed, the authorization key identifier AKID₁ corresponding to the authorization key AK₁ and the authorization key sequence number AK_SN₁ is determined when the authorization key AK₁ and the authorization key sequence number AK_SN₁ shared in the RSA-based authorization and 3-Way SA-TEK exchange processes are determined, and therefore the subscriber station 10 and the base station 20 may share the authorization key identifier AKID₁.

In a like manner of the first exemplary embodiment of the present invention, before the shared PAK lifetime expires, the subscriber station 10 and the base station 20 perform the RSA-based re-authentication to generate and share the new PAK₂, authorization key AK₂, and PAK sequence number PAK_SN₂. That is, in the second exemplary embodiment of the present invention, the subscriber station 10 and the base station 20 share the new PAK₂, authorization key AK₂, and the PAK sequence number PAK_SN₂ after performing the authentication of the base station 20 and the subscriber station 10 by using PKMv2 RSA-Request message 811-1, a PKMv2 RSA-Reply message 812-1, and a PKMv2 RSA-Acknowledgement message 813-1 in the like manner of the first exemplary embodiment of the present invention, and therefore detailed descriptions thereof will be omitted.

However, differing from the first exemplary embodiment of the present 15 invention, the PAK sequence number PAK_SN₂ shared by the subscriber station 10 and the base station 20 in the re-authentication process is allocated to be 4 bits in the second exemplary embodiment of the present invention. That is, the most significant 2 bits are set to be 0, and the remaining least significant 2 bits are set to be valid. In addition, when the new PAK sequence number PAK_SN₂ is generated after the RSA-based authorization process is successfully achieved, the least significant 2 bits are increased by one and modulo 4 is applied to the least significant 2 bits. For example, when the previous PAK sequence number PAK_SN₁ is ‘0001’, the newly allocated PAK sequence number PAK_SN₂ becomes ‘0010’. As described above, when the RSA-based re-authentication is successfully achieved, the subscriber station 10 and the base station 20 respectively have the two PAKs, PAK₁ and PAK₂ before the previous PAK sequence number PAK_SN₁ expires. In this case, the two PAKs are easily identified since the subscriber station 10 and the base station 20 have the different PAK sequence numbers PAK_SN₁ and PAK_SN₂ for the respective PAKs.

In addition, in a like manner of the first exemplary embodiment of the present invention, the subscriber station 10 and the base station 20 perform the 3-Way SA-TEK exchange process for the re-authentication to generate and share the new authorization key sequence number AK_SN₂ in the second exemplary embodiment of the present invention. That is, the subscriber station 10 and the base station 20 use the PKMv2 SA-TEK-Challenge message 814-1, the PKMv2 SA-TEK-Request message 815-1, and the PKMv2 SA-TEK-Response message 816-1 to share the new authorization key sequence number AK_SN₂ in a like manner of the first exemplary embodiment of the present invention, and therefore detailed descriptions thereof will be omitted.

However, differing from the first exemplary embodiment of the present invention, the authorization key sequence number AK_SN₂ newly shared by the subscriber station 10 and the base station 20 in the re-authentication process is allocated to be equal to the PAK sequence number PAK_SN₂ in the second exemplary embodiment of the present invention. That is, among the authorization key sequence number AK_SN₂ the most significant 2 bits are set to be 0, and the least significant 2 bits are set to be equal to that of the PAK sequence number PAK_SN₂.

As described above, a new authorization key identifier AKID₂ for identifying the authorization key AK₂ is generated by the authorization key AK₂ and the authorization key sequence number AK_SN₂ newly shared in the re-authentication process, so that the subscriber station 10 and base station 20 may share the authorization key identifier AKID₂. When the RSA-based re-authentication is achieved as described above, the subscriber station 10 and the base station 20 respectively have the two authorization keys AK₁ and AK₂ before the previous authorization key identifier AKID₁ expires. In this case, the two authorization keys may be easily identified since they have the different authorization key identifiers AKID₁ and AKID₂ for the respective authorization keys.

FIG. 7 shows a flowchart representing the authentication process according to the EAP-based authorization policy in the wireless portable Internet system according to the second exemplary embodiment of the present invention.

Referring to FIG. 5 and FIG. 7, when the subscriber station 10 and the base station 20 select the EAP-based authorization process as an authorization policy in the wireless portable Internet system according to the second exemplary embodiment of the present invention, the subscriber station 10 and the base station 20 use a PKMv2 EAP-Start message 711 and a PKMv2 EAP-Transfer message 712 to perform the authentication of the base station 20 and the subscriber station 10. In addition, a PKMV2 EAP-Transfer-Complete message 713 may be selectively used.

When the above authentication is achieved, the subscriber station 10 and the base station 20 share the PMK₁ and the authorization key AK₁.

When the PMK is newly generated in the re-authentication process according to the EAP-based authorization policy in the first exemplary embodiment of the present invention, the previous PMK is discarded and the new PMK is left to be used. Accordingly, a PMK sequence number PMK_SN is not defined since there is no case in which two PMKs exist.

In the second exemplary embodiment of the present invention, when the PMK is newly generated in the re-authentication process, the previous PMK is discarded and the new PMK is left to be used in the higher EAP method protocol according to the EAP-based authorization policy. However, the PMK sequence number PMK_SN for identifying the previous PMK and the new PMK is defined since the MAC layers of the subscriber station 10 and the base station 20 store and manage the previous PMK and the new PMK.

Therefore, the base station 20 generates the PMK sequence number PMK_SN₁ for identifying the PMK but does not distribute the PMK sequence number PMK_SN₁ to the subscriber station 10 in the EAP-based authorization process. In this case, the size of the PMK sequence number PMK_SN₁ generated by the base station 20 is 4 bits in a like manner of the PAK sequence number PAK_SN. In further detail, among the 4 bit-PMK sequence number PMK_SN₁, the least significant 2 bits are set to be 0, and the remaining most significant 2 bits are set to be valid, and therefore a used position of the PMK sequence number PMK_SN₁ is different from that of the PAK sequence number PAK_SN. In addition, the most significant 2 bits are increased by one by the base station 20 and modulo 4 is applied to the most significant 2 bits, whenever the PMK is updated. This is for preparing a case for performing both the RSA-based authorization and the EAP-based authorization processes, and it will be described later in the specification.

Subsequently, in a similar manner to the RSA-based authorization process described with reference to FIG. 6 according to the second exemplary embodiment of the present invention, the subscriber station 10 and the base station 20 may share the authorization key sequence number AK_SN₁ in the 3-Way SA-TEK exchange process, particularly by using a PKMv2 SA-TEK-Challenge message 714, and a 4 bit value which is equal to the PMK sequence number PMK_SN₁ is allocated as the authorization key sequence number AK_SN₁. The base station 20 performs the 3-way SA-TEK exchange process to transmit the PMK sequence number to the subscriber station 10 instead of performing the EAP-based authorization process. The size of the authorization key sequence number AK_SN₁ is 4 bits. In further detail, among the 4 bit-authorization key sequence number AK_SN_(I). the least significant 2 bits are set to be 0, and the remaining most significant 2 bits are set to be equal to the PMK sequence number PMK_SN₁.

Here, since the base station 20 allocates the authorization key sequence number AK_SN₁ having an equal value of the PMK sequence number PMK_SN₁ to the subscriber station 10 and shares it with the subscriber station 10, the subscriber station knows the PMK sequence number PMK_SN₁ by the authorization key sequence number AK_SN₁ distributed by the base station 20. Accordingly, the subscriber station 10 and the base station 20 may share the PMK sequence number PMK_SN₁.

In addition, differing from the first exemplary embodiment of the present invention, in a like manner of the RSA-based authorization process according to the second exemplary embodiment of the present invention, the authorization key identifier AKID₁ is used to identify the authorization key rather than using the authorization key sequence number AK_SN₁. The authorization key identifier AKID₁ is generated by using the authorization key sequence number AK_SN₁, the authorization key AK₁ the subscriber station MAC address SSID, and the base station identifier BSID. Therefore, in the EAP-based authorization process according to the second exemplary embodiment of the present invention, when the authorization key AK₁ and the authorization key sequence number AK_SN₁ are determined, the authorization key identifier corresponding to the AK₁ and AK_SN₁ is also determined so as to be shared by the subscriber station 10 and the base station 20.

In addition, the base station 20 transmits the PMK lifetime to the subscriber station 10 by using a PKMv2 SA-TEK-Response message 716 in the 3-way SA-TEK exchange process.

In a like manner of the RSA-based authorization process according to the second exemplary embodiment of the present invention, the subscriber station 10 performs the EAP-based re-authentication to generate and share the new PMK₂ and AK₂ before the shared PMK lifetime expires. That is, after performing the mutual equipment authentication or the user authentication by using a PKMv2 EAP-Start message 711-1 and a PKMv2 EAP-Transfer message 712-1, the subscriber station 10 and the base station may share the new PMK₂ and AK₂. At this time, a PKMv2 EAP-Transfer-Complete message 713-1 may be selectively used.

In a like manner of the RSA-based authorization process according to the second exemplary embodiment of the present invention, the subscriber station 10 and the base station 20 perform the 3-Way SA-TEK exchange process for the re-authentication, generate the authorization key sequence number AK_SN₂ and share the AK_SN₂. That is, the subscriber station 10 and the base station 20 use a PKMv2 SA-TEK-Challenge message 714-1, a PKMv2 SA-TEK-Request message 715-1, and a PKMv2 SA-TEK-Response message 716-1 to share the new authorization key sequence number AK_SN₂. In this case, the base station 20 allocates the authorization key sequence number AK_SN₂ newly shared by the subscriber station 10 and the base station 20 in the re-authentication process so that it may have the same value as the PMK sequence number PMK_SN₂. The base station 20 sets the PMK sequence number PMK_SN₂ newly generated in the re-authentication process by the base station 20 to be 4 bits in a like manner of the previous PMK sequence number PMK_SN₁. However, since the EAP-based authorization process has been achieved and the new PMK sequence number PMK_SN₂ has been generated, the most significant 2 bits of the PMK sequence number PMK_SN₂ are increased by one and the modulo 4 is applied to the most significant 2 bits of the new PMK sequence number PMK_SN₂ For example, when the previous PMK sequence number PMK_SN₁ is ‘0010’, the new PMK sequence number PMK_SN₂ becomes ‘0011’. When the EAP-based re-authentication is achieved, the subscriber station 10 and the base station 20 respectively have the two PMKs PMK₁ and PMK₂ before the previous PMK sequence number PMK_SN₁ expires. In this case, the two PMKs may be easily identified since the different PMK sequence numbers PMK_SN₁ and PMK_SN₂ are provided for the respective PMKs.

Subsequently, the subscriber station 10 may know the new PMK sequence number PMK_SN₂ by the authorization key sequence number AK_SN₂ shared with the base station 20, and therefore the subscriber station 10 and the base station 20 share the PMK sequence number PMK_SN₂ because the authorization key sequence number AK_SN₂ is equal to the PMK sequence number PMK_SN₂. Therefore, the PMK sequence numbers PMK_SN₁ and PMK_SN₂ for identifying the previous PMK₁ and the new PMK₂ may be separately provided to be shared.

In addition, the new authorization key identifier AKID₂ for identifying the authorization key AK₂ Is generated by the authorization key AK₂ and the authorization key sequence number AK_SN₂ newly shared in the re-authentication process, and therefore it may be shared by the subscriber station 10 and the base station 20. When the EAP-based re-authentication process is achieved as described above, the subscriber station 10 and the base station 20 respectively have the-two authorization keys AK₁ and AK₂ before the previous authorization key identifier AKID₁ expires. In this case, the two authorization keys may be easily distributed since the different authorization key identifiers AKID₁ and AKID₂ are provided for the respective authorization keys.

It has been described that one of the RSA-based authorization process and the EAP-based authorization process is performed, and it will now be described that the RSA-based authorization process and the EAP-based authorization process or the authenticated EAP-based authorization process are performed.

When the RSA-based authorization process and the EAP-based authorization process or the authenticated EAP-based authorization processes are performed, referring to FIG. 6, the base station 20 and the subscriber station 10 may share the PAK₁, PAK lifetime, and the PAK sequence number PAK_SN₁ in the RSA-based authorization processes 611, 612, and 613 as described above, and subsequently, referring to FIG. 7. They may share the PMK₁ in EAP-based authorization processes 711, 712, and 713 as described above. Here, when the authenticated EAP-based authorization process is performed rather than performing the EAP-based authorization processes 711, 712, and 713, they may share the PMK₁ in the authenticated EAP-based authorization process. The PKMv2 EAP-Start message 711 and the PKMv2 EAP-Transfer-Complete message 713 are selectively used in the authenticated EAP-based authorization process. A PKMv2 Authenticated-EAP-Transfer message including a message authentication function is used instead of using the PKMv2 EAP-Transfer message 712 of the EAP authentication process.

Since the authorization key AK1 is generated by combining the shared PAK₁ and PMK₁, the subscriber station 10 and the base station 20 may share 10 the AK₁. In this case, the size of the PAK sequence number PAK_SN₁ shared by the subscriber station 10 and the base station 20 is 4 bits, the most significant 2 bits are set to 0, and the least significant 2 bits are set to be valid.

Subsequently, referring to FIG. 6 and FIG. 7, the base station 20 generates the authorization key sequence number AK_SN₁ in the 3-Way SA-TEK exchange process and allocates the AK_SN₁ to the subscriber station 10. Since the base station 20 has the PAK sequence number PAK_SN₁ In the RSA-based authorization process and the PMK sequence number PMK_SN₁ in the EAP-based authorization process, the authorization key sequence number AK_SN₁ is generated by a sum of the bits of the PAK sequence number PAK_SN1 and the PMK sequence number PMK_SN₁. That is, different bits are used in the PAK sequence number PAK_SN₁ and the PMK sequence number PMK_SN1 since the PAK sequence number PAK_SN₁ uses the least significant 2 bits among the 4 bits and the PMK sequence number PMK_SN₁ uses the most significant 2 bits among the 4 bits. Therefore, contents of the PAK sequence number PAK_SN₁ and PMK sequence number PMK_SN₁ may be provided in the authorization key sequence number AK_SN₁ even when the bits of them are added.

As described, since the base station 20 distributes the authorization key sequence number AK_SN₁ to the subscriber station 10 and shares the AK_SN₁ with the subscriber station 10, the subscriber station 10 may indirectly know PMK sequence number PMK_SN₁ by the authorization key sequence number AK_SN₁ distributed by the base station 20. Accordingly, the subscriber station 10 and the base station 20 may share the PMK sequence number PMK_SN₁.

Subsequently, the authorization key identifier AKID₁ is used to identify the authorization key instead of using the authorization key sequence number AK_SN₁. and the authorization key identifier AKID₁ is generated by using the authorization key sequence number AK_SN1 the authorization key AK₁, the subscriber station MAC address SSID, and the base station identifier BSID, which has been described above, and therefore detailed descriptions will be omitted.

The subscriber station 10 and the base station 20 share the PAK lifetime in the RSA-based authentication process, and share the PMK lifetime in the 3-Way SA-TEK exchange process.

When the RSA-based authorization process and the EAP-based authorization process or the authenticated EAP-based authorization process are performed, the RSA-based re-authentication process or the EAP-based re-authentication process may be independently performed since the previous PAK lifetime and PMK lifetime have independent values.

The RSA-based re-authentication process is performed before the PAK lifetime expires, the subscriber station 10 and the base station 20 may share the new PAK₂ and PAK sequence number PAK_SN₂ in the RSA-based re-authentication process, share the new authorization key sequence number AK_SN₂ in the 3-Way SA-TEK exchange process which is subsequently performed after the RSA-based re-authentication process, and use the shared PMK₁ and PMK sequence number PMK_SN₁ to generate and share the new authorization key AK₂ and the authorization key identifier AKID₂.

In addition, when the EAP-based re-authentication process is performed before the PMK lifetime expires, the subscriber station 10 and the base station 20 may share the new PMK₂ and PMK sequence number PMK_SN₂ in the EAP-based re-authentication process, share the new authorization key sequence number AK_SN₂ in the 3-Way SA-TEK exchange process which is subsequently performed after the EAP-based re-authentication process, and use the shared PAK₁ and PAK sequence number PAK_SN₁ to generate and share the new authorization key AK₂ and the authorization key identifier AKID₂.

When the various re-authentication processes are performed, as described above, the two PAKs PAK₁ and PAK₂ may be identified by using the PAK sequence numbers PAK_SN, and PAK_SN₂, the two PMKs PMK₁ and PMK₂ may be identified by using the PMK sequence numbers PMK_SN₁ and PMK-SN₂ and the two authorization keys AK₁ and AK₂ may be identified by using the authorization key identifiers AKID₁ and AKID₂. The PAK sequence number PAK_SN₂, the PMK sequence number PMK_SN₂, and the authorization key sequence number AK_SN₂ are set to be 4 bits.

The re-authentication processes may be easily understood by referring to FIG. 3 and FIG. 4, and therefore detailed descriptions thereof will be omitted.

As described above, the problems of the respective key identifiers and the PMK lifetime defined in the PKMv2 of the conventional IEEE 802.16e wireless MAN-based portable Internet service are resolved according to the second exemplary embodiment of the present invention. That is, when the lifetime for key is provided in the EAP method protocol, this lifetime is used as the PMK lifetime, but when the lifetime for key is not provided in the EAP method protocol, the lifetime defined by the vendor is used as the PMK lifetime. Therefore, the EAP-based re-authentication may be efficiently performed.

In addition, the efficiency is increased when the identifier is transmitted in the radio link since the sizes of PAK identifier, PMK identifier, and authorization key identifier are reduced from 64 bits to 4 bits.

In addition, the authorization key sequence number for determining the authorization key identifier is generated by the PAK identifier and the PMK identifier, the base station 10 generates the PAK identifier and the PMK identifier so that they are increased by one whenever the authorization key is updated, and the base station allocates the PAK identifier and the PMK identifier to the subscriber station 10, and therefore the two authorization keys may be identified by the authorization key identifier.

When the subscriber station authenticated in the RSA-based authorization or in the EAP-based authorization performs a handover to a new base station 21, the authorization key of the base station 20 providing a current service is different from the authorization key of the new base station 21. The authorization key identifier AKID is used to identify the above different authorization keys. Since the authorization key identifier AKID is generated by using the authorization key sequence number AK_SN, authorization key AK, subscriber station MAC address SSID, and base station identifier BSID, the new base station 21 is not required to additionally perform the RSA-based authorization process or the EAP-based authorization process when the subscriber station 10 finishes the handover. In addition, the handover may be quickly performed since it is not required to allocate the authorization key identifier. That is, when the subscriber station 10 achieves the handover, since the authorization key identifier AKID_(old) of the base station 20 having provided the service is different from the authorization key identifier AKID_(new) of the new base station 21, the new base station 21 is not required to additionally transmit a field for identifying the authorization key to the subscriber station 10, and then the handover process may be quickly performed at the new base station 21.

In addition, when the subscriber station 10 achieves the handover, and the RSA-based re-authentication and the EAP-based re-authentication are not performed between the subscriber station 10 and the base station 21 to which the subscriber station is handed over, the subscriber station 10 uses the authorization key sequence number used by the base station 20 as the authorization key sequence number of the base station 21 to which the subscriber station is handed over.

While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

The effects of the IEEE 802.16 MAN-based wireless portable Internet system according to the exemplary embodiment of the present invention are as follows:

First, when the EAP-based authorization is performed, the EAP-based re-authentication may be efficiently performed since the PMK lifetime is provided from the EAP method protocol or is defined by the vendor.

Second, the respective PAK, PMK, and authorization key may be distinguished since the base station generates the PAK identifier, PMK identifier, and authorization key identifier and transmits them to the subscriber station.

Third, radio resources may be effectively used since the small amount of radio resources are used to transmit the identifiers in a radio link by reducing the size of the PAK identifier, PMK identifier, and authorization key sequence number.

Fourth, according to the second exemplary embodiment of the present invention, the PMK identifier may be automatically known by using the authorization key sequence number without additionally transmitting the PMK identifier since the authorization key sequence number is generated by a combination of the PAK identifier and the PMK identifier.

Fifth, according to the second exemplary embodiment of the present invention, there is a merit in that the authorization key sequence number of a small size is transmitted to identify the authorization key since the authorization key sequence number and the authorization key identifier for the authorization key are separately managed.

Sixth, according to the second exemplary embodiment of the present invention, when the subscriber station successfully performs the handover, a quick handover maybe performed at the base station to which the subscriber station is handed over. 

What is claimed is:
 1. A method of sharing information for identifying an authorization key (AK) with a base station in a subscriber station, the method comprising: at the subscriber station, sharing a root key with the base station by performing an authentication with the base station; at the subscriber station, sharing the AK derived from the root key with the base station; at the subscriber station, sharing an AK sequence number of the AK with the base station; and at the subscriber station, sharing an AK identifier (AKID) of the AK with the base station, wherein the AK sequence number is generated at the subscriber station from a sequence number of the root key, and wherein the AKID is generated at the subscriber station from a parameter comprising the AK, the AK sequence number, a medium access control (MAC) address of the subscriber station, and a base station identifier (BSID) of the base station.
 2. The method of claim 1, wherein the authentication comprises an extensible authentication protocol (EAP) based authentication, and the root key is a pairwise master key (PMK).
 3. The method of claim 2, further comprising sharing a PMK sequence number of the PMK with the base station.
 4. The method of claim 3, wherein the PMK sequence number has 4 bits, and wherein 2 bits among the 4 bits are zero bits, and the other 2 bits are effective bits.
 5. The method of claim 2, wherein the AK sequence number is the same as a PMK sequence number of the PMK.
 6. The method of claim 5, wherein the PMK sequence number has 4 bits, and wherein 2 bits among the 4 bits are zero bits, and the other 2 bits are effective bits.
 7. An authentication apparatus of a subscriber station, the apparatus comprising: at least one processor configured to perform an authentication with a base station, and to obtain a context associated with the authentication, wherein the context comprises: an AK derived from a root key that is generated by performing the authentication with the base station; an AK sequence number of the AK, the AK sequence number being generated by a sequence number of the root key; and an AK identifier (AKID) of the AK, the AKID being generated by a parameter comprising the AK, the AK sequence number, a medium access control (MAC) address of the subscriber station, and a base station identifier (BSID) of the base station.
 8. The apparatus of claim 7, wherein the authentication comprises an extensible authentication protocol (EAP) based authentication, and the root key is a pairwise master key (PMK).
 9. The apparatus of claim 8, wherein the context further comprises a PMK sequence number of the PMK.
 10. The apparatus of claim 9, wherein the PMK sequence number has 4 bits, and wherein 2 bits among the 4 bits are zero bits, and the other 2 bits are effective bits.
 11. The apparatus of claim 8, wherein the AK sequence number is the same as a PMK sequence number of the PMK.
 12. The apparatus of claim 11, wherein the PMK sequence number has 4 bits, and wherein 2 bits among the 4 bits are zero bits, and the other 2 bits are effective bits.
 13. An authentication apparatus of a base station, the apparatus comprising: at least one processor configured to perform an authentication with a subscriber station, and to obtain a context associated with the authentication, wherein the context comprises: an AK derived from a root key that is generated by performing the authentication with the subscriber station; an AK sequence number of the AK, the AK sequence number being generated by a sequence number of the root key; and an AK identifier (AKID) of the AK, the AKID being generated by a parameter comprising the AK, the AK sequence number, a medium access control (MAC) address of the subscriber station, and a base station identifier (BSID) of the base station.
 14. The apparatus of claim 13, wherein the authentication comprises an extensible authentication protocol (EAP) based authentication, and the root key is a pairwise master key (PMK).
 15. The apparatus of claim 14, wherein the context further comprises a PMK sequence number of the PMK.
 16. The apparatus of claim 15, wherein the PMK sequence number has 4 bits, and wherein 2 bits among the 4 bits are zero bits, and the other 2 bits are effective bits.
 17. The apparatus of claim 14, wherein the AK sequence number is the same as a PMK sequence number of the PMK.
 18. The apparatus of claim 17, wherein the PMK sequence number has 4 bits, and wherein 2 bits among the 4 bits are zero bits, and the other 2 bits are effective bits. 